Recently, thanks to a remarkable development of information and communication technology and semiconductor technology, the prevalence and use of various electronic devices is rapidly increasing. Especially, recent electronic devices have been developed to be able to communicate while being carried on the body. A user receives a communication service by subscribing to the network which the user wants among various networks in order to communicate using the electronic device. Typically, the electronic device is mostly equipped with a network lock function at the time of release. Also referred to as a factory lock, a network lock is a function which may limit the use from the rest of networks except a particular network among networks.